This invention relates to silenced impact driven tools and to silenced impacting apparatus associated therewith, and particularly to internal silencing means wholly contained within the impact driven tools and impacting apparatus therefor.
Impact driven tools generally comprise a bitter end and collar adapted to be received within an impacting apparatus, and a shank extending from the collar to a tip. The tip may be sharpened to provide the working surface of the tool, or may be adapted to receive a replaceable sharpened tip providing the working surface of the tool as disclosed in my U.S. Pat. No. 3,655,244. The impacting apparatus, commonly known as an air hammer or pneumatic drill, in which the impact driven tools are used, generally comprises means for holding the bitter end and collar of the tool, and hammer means pneumatically driven to strike the bitter end of the tool. The combination of an impacting apparatus and impact driven tool is a common sight around construction jobs and is used to break pavement, concrete, and the like.
The impacting apparatus and impact driven tools are extremely noisy in operation, and constitute a disturbance, annoyance and nuisance. The problem is sufficiently acute that the noise levels produced by these tools are now being regulated by law to not exceed certain limits as expressed in decibels. However, the manufacturers of impact driven tools and impacting apparatus are experiencing a great deal of difficulty in meeting the noise level standards.
When an impact driven tool is struck by the hammer of an impacting apparatus, two types of sound producing motions are created within the impact driven tool. First, a lateral mode of vibration is created, and the lateral mode consists generally of motion with respect to the axis of the tool. My U.S. Pat. No. 3,848,931 deals effectively with the lateral mode of sound producing motion.
The second type of motion is in the longitudinal or axial mode, i.e., along and parallel to the axis of the impact driven tool. This type of sound producing motion is also created in the hammer of the impacting apparatus used to strike the tool.